Vision technology is of critical significance for achieving a high equipping precision in the automatic equipping of substrates, particularly printed circuit boards or ceramic substrates, with SMD components for surface mounting (SMD=Surface Mounted Devices). The vision technology thereby comprises a substrate vision system and a components vision system. The substrate vision system acquires reference marks or circuit structures of the substrate with a CCD camera. A computer determines the exact position of the substrate (X, Y, .phi.) and a potentially existing distortion from the position of the reference marks. For equipping, all equipping positions (X, Y, .phi.) are correspondingly corrected.
The components vision system is composed of CCD camera, illumination and ground glass screen. The corresponding components vision module is placed on the offering table of the delivery modules. The equipping head places the components onto the ground glass screen such that their terminals can be recognized. The positional deviation of the terminals is determined, for example with a stored pattern, by optoelectronic correlation of all terminals. Using the values of the positional deviations, the automatic equipping unit corrects the equipping paths and the rotational angle to the exact equipping position (X, Y, .phi.) previously determined with a substrate vision system.
The above-described optoelectronic centering of components with the assistance of a components vision system presents considerable difficulties given some types of component, particularly given flip chips, bare chips and ball grid arrays. When the terminals whose position is to be recognized are viewed as useful structures and all other optically emerging structures of the components are viewed as unwanted structures, the unwanted structures are also at least partially clearly imaged. A reliable image evaluation is made more difficult or entirely prevented as a result thereof. Given, for example, flip chips, the aluminum interconnects, the silicon nitride structures and the silicon oxide structures are to be cited as unwanted structures. The bodies and edges of the components are also to be viewed as unwanted structures.
European reference, A, 0 341 806 has disclosed a means for the inspection of printed circuit boards with SMD components that can be moved across the printed circuit board. The means contains a cylindrical shaft in which two ring light illuminations lying above one another as well as four cameras are arranged. The ring light illuminations are each divided into 4 segments whose middle regions lie in the principal coordinate directions of the printed circuit board proceeding from the center. The cameras are likewise obliquely directed onto the printed circuit board proceeding concentrically from the outside. Their middle axes coincide with the coordinate directions.
The means serves the purpose of checking the presence and position of the components soldered on the printed circuit board. In particular, the means is directed such onto the lateral edges of the component that the ring light segment pointing in this direction and the camera allocated to this are respectively activated. The means likewise serves the purpose of determining the position of solder points on the printed circuit board. This occurs by activating two of the segments lying opposite the solder point and a camera directed perpendicular thereto.